Hydrocarbon fueled internal combustion engines have been proposed that utilize cryogenic liquid, storable liquid, or highly compressed stored gaseous oxidants. Ideally, only incidental compression is to be done in the working cylinder of these non-air breathing internal combustion engines. Liquids (fuel and/or oxidant) injected into the cylinder too early in the cycle will vaporize prior to top dead center (TDC) and, therefore, present an undesirable back pressure (compression) on the piston, connecting rod, and crankshaft. Liquids injected too late will not vaporize and hence combust, until after TDC and, therefore, waste valuable expansion ratio.
A finite length of time will be required to vaporize liquids injected into the engine combustion chamber. Complete combustion requires complete vaporization. Vaporization time will be somewhat uncertain and depends upon many factors: degree of liquid atomization when injected, nature of the liquid, method and location of injection, temperature and thermal characteristics of the combustion chamber, amount and temperature of the clearance gas, etc.